The present invention relates to an electromagnetic valve, particularly for controlling a fuel injector or for regulating the pressure of a high-pressure fuel accumulator, comprising a casing, an electromagnet formed of the yoke and an electromagnetic coil housed in the latter, and an armature in one or more parts.
The invention also relates to a fuel injector or a high-pressure fuel accumulator fitted with an electromagnetic valve as defined above.
Such an electromagnetic valve is used amongst other things for controlling the pressure of the fuel in the control chamber of a fuel injector, for example of an injector of a common rail injection system. With such electromagnetic valves, with the pressure of the fuel in the control chamber of the electromagnetic valve, controls the movement of the valve closure member (injector needle) with which the injection nozzle of the fuel injector is opened or closed.
According to document DE 198 32 826 A1, an electromagnetic valve for controlling a fuel injector is known. The electromagnetic valve comprises a casing accommodating an electromagnet, and a movable armature acted upon by the force developed by a valve spring, and a closure member made on the armature or interacting with the latter and pushed against a seat of the electromagnetic valve by the force developed by the valve spring. The electromagnet makes it possible to open and close the electromagnetic valve in order to thus regulate the outlet of fuel from the control chamber.
In the case of the known electromagnetic valve according to document DE 198 32 826 A1 above, the armature has a portion that is in relief in the shape of a collar on its face turned towards the electromagnet and that rests against a casing portion surrounding the electromagnet in the final position when the electromagnet is attracted; the height of this collar defines the residual air gap between the electromagnet and the transverse face of the armature.
Document U.S. Pat. No. 5,295,627 A1 describes an electromagnetic valve having a thin disk between the armature and an electromagnet. This thin disk limits the travel along which the armature can come closer to the electromagnet and thus defines the residual air gap. This disk is made of a non-magnetizable material and it is called a residual air gap disk.
Document DE 10 131 199 A1 describes an electromagnetic valve in which the transverse face of the armature or the polar surface of the electromagnet turned in a corresponding manner comprises a portion in relief made of a non-magnetoconducting material, for example a coating defining the minimum distance between the magnetoconducting surfaces of the electromagnet and the armature.
All these exemplary embodiments have in common that they have a “residual air gap”, that is to say that they define a non-magnetoconducting distance between the armature and the electromagnet which prevents the armature from sticking against the electromagnet. The fuel in the gap between the armature and the electromagnet operates as the elements come closer like a hydraulic damper. The disk forming a residual air gap between the transverse face and the electromagnet and the opposite transverse face of the armature also makes it possible to adjust this hydraulic damping.